Table of Contents

Overview

South Carolina's Sea Level Is Rising

And It’s Costing Over $2 Billion

The sea level off South Carolina’s coast is up to 10 inches higher than it was in 1950.1 This increase is mostly due to ice melt, and it’s causing major issues. In the 1970s the city of Charleston experienced an average of 2 days of flooding per year, but now it is projected that the City could experience 180 days of tidal flooding by 2045.2 Across the state, flooding has increased 75% since 2000.3 Because of its low elevation, Charleston’s medical district is exceptionally vulnerable to flooding. During flood events, areas of MUSC become inaccessible, making it impossible to evacuate or move patients.4

There are already over 90,000 properties at risk from frequent tidal flooding in South Carolina.5 The state is planning over $2 billion in sea level rise solutions, which include beach renourishment, seawalls, drainage improvements, and raising roads.

Sea level rise is speeding up

The sea level around Charleston, South Carolina, has risen by 10 inches since 1950. Its speed of rise has accelerated over the last ten years and it’s now rising by about 1 inch every 2 years.1 Scientists know this because the sea level is measured every 6 minutes using equipment like satellites, floating buoys off the coast, and tidal gauges to accurately measure the local sea level as it accelerates and changes.6

Created with Highcharts 6.2.0

SEA LEVEL MEASUREMENT FROM CHARLESTON AREA TIDE GAUGE SINCE 1950

Causes & Complications

Why Are Sea Levels Rising?

While there are four main causes of sea level rise in South Carolina, land sinkage is the largest contributor.7 Because the land is getting lower each year, due to a process called subsidence, South Carolina is particularly vulnerable to an increased rate of sea level rise in the future. Click here to learn more about these causes.

How Land Sinkage Increases Sea Level Rise

Most flooding happens during the fall

King tides are unusually high tides that generally occur during a new for full moon, or when the sun, moon, and earth align. In some places, king tides are brought on by changes in the weather and ocean patterns. In places like Charleston, king tides are typically nearly a foot and a half higher than normal.1 Add that to the 10 inches of sea level rise since 1950, and you end up with flooding even on sunny days.

Solutions aren’t simple

Whereas in In the 2000,1970s Charleston experienced just 2 days, on average, of tidal flooding per year, the city saw 9 days in 2016.3 Today, flooding across the state has increased by 75%.3 In Beaufort County, SC, the ground is sinking approximately 1 inch lower every 20 years.8 This makes buildings and streets more vulnerable to the rising sea and solutions more complicated, but also more urgent.

Charleston is at the point in history where many of our human activities, pollution, deforestation, and urbanization have diminished the resilience of natural communities.

Phillip Dustan, Professor, Department of Biology, College of Charleston; Faculty, University of Charleston

Forecast

What's the Future of Sea Level Rise?

In the last decade, the speed at which South Carolina’s sea level is rising has increased, and is now rising by as much as 1 inch every 2 years.1 Around Charleston, it took around 26 years for the sea level to rise 6 inches.1 Scientists now forecast that in the next 13 years, the speed will double, causing the sea to rise by another 6 inches.9

Scientists are not certain how fast the ocean will warm and ice will melt. They expect water levels to continue to rise faster, but are not sure just how fast. Therefore scientists from the National Oceanic and Atmospheric Administration (NOAA) and the US Army Corps of Engineers (USACE) have made predictions based on ranges from low to high.

Below you can see the range of the NOAA and USACE high and intermediate forecasts for various locations around South Carolina.10 Currently, the USACE high forecast, seen as the darkest red line, is the most likely projection.

Charleston

Created with Highcharts 6.2.0Charleston Sea Level Rise Forecasts

Sea level will rise, storms will increase, and rainfall will be more intense as evidenced by recent hurricane-driven flooding disasters. This is the new normal and it is imperative to plan for these eventualities.

Phillip Dustan, Professor, Department of Biology, College of Charleston; Faculty, University of Charleston

Flooding

Why Are Floods More Frequent?

When the ocean rises high enough, high tides cause flooding even on sunny days. Even though the sea level has only risen by around 4 inches, tidal flooding has increased by 75% in some areas of South Carolina since 2000.2

How sea level rise affects South Carolina

Flooding even when there’s no rain

Drainage systems are designed to channel excess rainwater from the streets and drain it into the sea. But with the pressure from rising sea levels and higher tides, seawater can get pushed into these pipes and spill out into the streets. This causes flooding even on days without rain.

Drainage Under Normal Tidal Conditions

Drainage With King Tide / Sea Level Rise

Increased storm surge flooding

Unfortunately, slightly higher sea levels make hurricanes even more damaging. Just a few more inches of sea level rise allow a hurricane to push more water onto the land, even if the hurricane itself doesn’t make landfall.

Hurricane Irma, 2017

Higher sea levels create a higher launching point for storm surge. These small changes in sea level rise are enough to turn what were 100-year storm surges into much more frequent events. In fact, in a third of 55 coastal sites studied throughout the US, 100-year storm surges will be 10-year or more frequent events by 2050.11

This means that in many coastal cities, if you bought a house with a 30-year mortgage today, by the time you paid off your mortgage you could be experiencing extreme 100-year storm surges ten times more frequently due to sea level rise alone. This does not include the added risk of more intense storms resulting from warmer water and a warmer atmosphere, which could further increase storm surge damage.

In 2017, Hurricane Irma devastated parts of South Carolina with powerful storm and caused $51 billion in damages.12 Without sea level rise, Hurricane Irma’s 5.6 foot storm surge would have been lower.13

Hurricane Irma, 2017

Costs

What's at Risk in South Carolina?

There’s a lot at risk from sea level rise and flooding in South Carolina. Charleston is home to many hospitals which have roads nearby that flood, making it impossible at times for emergency vehicles to get to these hospitals quickly.4 In addition to this and the residential areas that flood, the city also has historic areas that are becoming inundated with more water, more frequently. As sea level continues to rise, these issues will only become worse.

Schools & Hospitals

Flooding can impact critical community resources such as neighborhood schools and hospitals.

Homes & Cars

Storm surges or flooding can damage the underside of your car or the first level of your home.

Beaches

Rising seas increase the speed of beach erosion, pulling more sand from the beach into sea. Replacing the sand is possible, but expensive.

In Charleston there are 5,543 residential properties already at risk from repeated tidal flooding, by 2033 that number will increase to 8,349 as sea levels rise. In Mount Pleasant, 3,549 properties at risk will turn into 5,347 within 15 years. In Kiawah Island there are 850 properties at risk, which will become 1,355. And in Hilton Head Island, there are 1,180 properties at risk, which will increase to 2,603 by 2033. Click here to explore other coastal communities in South Carolina that are at risk at FloodiQ.com.

South Carolina is spending over $2 billion

Some cities have sufficient resources to deal with this problem while others do not. South Carolina will need solutions at the individual, local, state, and federal levels to protect its coastal communities.